1. Field of the Invention
The present invention relates to a fan motor in a refrigerator, and more particularly to a refrigerator capable of controlling a fan motor, in which the fan motor rpm is controlled according to a cooling load.
2. Prior Art
Generally, a refrigerator cooling system comprises a compressor for compressing a refrigerant, a condenser for condensing the compressed refrigerant radiating heat outward, a capillary tube for changing the condensed refrigerant into a low-temperature and low-pressure state, an evaporator for vaporizing refrigerant by absorbing heat in the refrigerator, and a cabinet having a freezer compartment and fresh food compartment which are partitioned from each other by a wall.
The cooling process of a conventional refrigerator is shown in FIG. 1. The refrigerant is compressed to high-temperature and high-pressure by a compressor 11 and is condensed by radiating heat outward at a condenser 12. The condensed refrigerant in the state of low-temperature and low-pressure passes through a capillary tube 13 and goes into an evaporator 14. The refrigerant is vaporized in the evaporator 14 by absorbing heat from surrounding air. The refrigerant passed through the evaporator 14 is inputted into the compressor 11 completing refrigerant circulation.
During the refrigerant circulation, heat is transferred from surrounding air to the refrigerant at the evaporator 14 and radiated outward at the condensor 12. The air surrounding the evaporator 14 cools by loosing heat, causing the cooling effect of a refrigerator.
The generated cool air is supplied to the freezer compartment and fresh food compartment by a cooling fan 15 for cooling the freezer compartment and fresh food compartment. A fan motor 16 operates the cooling fan 15 by a predetermined rpm, and the rate of cool air supply is controlled by the rpm of the fan motor 16.
An alternating current (AC) motor has been conventionally used to operate the cooling fan which is installed in the rear of the refrigerator. The rpm of the AC motor remains constant, regardless of the cooling load. Hence, the use of the AC motor offer little flexibility in circulating the cool air in the varying condition of the refrigerator.
That is, when the cooling load of the refrigerator increases, it is difficult to cool the refrigerator quickly with the AC motor, and to provide constant temperature environment for foods which are affected by variant temperature. Additionally, the AC motor maintained at high rpm consumes considerable amount of electric power even at the low cooling load of the refrigerator, causing inefficiency of the refrigerator.